Physiology
Nerve System
Behrouz Mahmoudi
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• Brain– Meninges are layers of non-nervous tissue that
surround and protect the brain and spinal cord.
the outermost of the three layers of the meninges
that surround the brain and spinal cord. is a thick,
durable membrane, closest to the skull.
It provides a cushioning effect for the central
nervous system
very delicate membrane. firmly adheres to
the surface of the brain and spinal cord,
following the brain's minor contours
The subarachnoid space is the space that normally
exists between the arachnoid and the pia mater,
which is filled with cerebrospinal fluid.
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CNS: CENTRAL NERVE SYSTEM
There are three major divisions of the brain:
Cerebral Cortex
telencephalon
Basal Ganglia
The Limbic System
Forebrain:
Thalamus
diencephalon
Hypothalamus
Cerebral Cortex surrounds the cerebral hemispheres, commonly imagined when an
image/thought of the brain is recalled from memory.
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The cerebral cortex is commonly referred to as gray matter, due to the
predominance of cells appears grayish brown. Consist cell bodies.
The neurons of the cerebral cortex are connected to other neurons within the brain via
millions of axons located beneath the cortex. This area is white in color due to the
concentration of myelin; it is often called white matter
Left
hemisphere
controls
linguistic
consciousness, the right half of the body, talking,
reading,
writing,
spelling,
speech
communication,
verbal
intelligence
and
memories, and information processing in the
areas of math, typing, grammar, logic, analytic
reasoning, and perception of details.
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The right hemisphere is associated with 'unconscious' awareness (in the
sense it is not linguistically based), perception of faces and patterns,
comprehension of body language and social cues, creativity and insight,
intuitive reasoning, visual-spatial processing, and holistic comprehension.
Communication between the two hemispheres takes
place through the corpus callosum
Basal Ganglia: The basal ganglia are a collection of subcortical nuclei they are involved with
the control of movement. Parkinson's disease has an effect upon the basal ganglia resulting
in poor balance
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The Limbic System: is a collection of brain structures involved with emotion,
motivation, multifaceted behavior, and memory storage and recall. The
hippocampus (sea horse) and the amygdala (almond), along with portions
of the hypothalamus, thalamus, caudate nuclei, and septum function
together to form the limbic system.
Thalamus: is the relay station for incoming
sensory signals and outgoing motor signals
passing to and from the cerebral cortex.
With the exception of the olfactory sense,
all sensory input to the brain connected to
nerve cell clusters (nuclei) of the thalamus.
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Hypothalamus:
is comprised of distinct areas and nuclei which control vital survival
behaviors and activities such as: eating, drinking, temperature regulation,
sleep, emotional behavior, and sexual activity.
The autonomic nervous system and endocrine system are controlled by
the hypothalamus.
Neurosecretory cells released by the hypothalamus act upon the anterior
pituitary gland which then secretes its hormones.
Midbrain, The Mesencephalon:
Two primary parts comprise the midbrain: the tectum and the tegmentum.
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Tectum: The primary structure of the tectum include the superior
colliculi and the inferior colliculi. The superior colliculi form part of
the visual system. The inferior colliculi are part of the auditory
system
Tegmentum:It receives sensory information
and is involved with attention, sleep and
arousal, muscle tonus, control sequences of
movements constituting species-typical
behavior.
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Metencephalon Cerebellum (little brain)
Pons
The Hindbrain
Myelencephalon: comprised of the medulla oblongata (oblong marrow)
Cerebellum (little brain): It serves as
a reflex center for the coordination and
precise maintenance of equilibrium.
Voluntary and involuntary bodily
movements are controlled by the
cerebellum.
Visual, auditory, vestibular, and
somatosensory information is received
by the cerebellum, as is information on
the movements of individual muscles.
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Pons: The pons contain a portion of the reticular formation as well as
nuclei believed important in the role of sleep and arousal
Medulla oblongata:
is the control center for cardiac, vasoconstrictor,
and respiratory functions. Reflex activities,
including vomiting, are controlled by this
structure of the hindbrain. Appearing as a
pyramid-shaped enlargement of the spinal cord,
damage to this area typically results in immediate
death.
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The spinal cord:
is the main pathway for information connecting the brain and
peripheral nervous system.
The human spinal cord is protected by the
bony spinal column called vertebrae.
The spinal cord is located in the vertebral
foramen and is made up of 31 segments: 8
cervical, 12 thoracic, 5 lumbar, 5 sacral and 1
coccygeal. A pair of spinal nerves leaves each
segment of the spinal cord
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The nerves which carry information from the brain to muscles are
called Motor Neurones. The nerves which carry information from
the body back to the brain are called Sensory Neurones.
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The spinal cord is surrounded by a clear fluid called Cerebral
Spinal Fluid (CSF), that acts as a cushion to protect the delicate
nerve tissues against damage from banging against the inside of
the vertebrae
The brain and spinal cord are referred to as
the Central Nervous System, whilst the nerves
connecting the spinal cord to the body are
referred to as the Peripheral Nervous System.
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Peripheral Nervous System
consists of the nerves and ganglia outside of the brain and
spinal cord. The main function of the PNS is to connect the
central nervous system (CNS) to the limbs and organs. Unlike
the CNS, the PNS is not protected by the bone of spine and
skull, or by the blood-brain barrier, leaving it exposed to
toxins and mechanical injuries.
The peripheral nervous system is divided
into the somatic nervous system and the
autonomic nervous system.
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Cranial Nerves
The nuclei of cranial
nerves I and II lie in
the forebrain and
thalamus,
respectively, and are
thus not considered to
be true cranial nerves
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Autonomic Nervous System (ANS)
• The autonomic or involuntary nervous system
is that portion of the nervous system which
regulates the activity of cardiac muscle,
smooth muscle, and the glands.
• The ANS has two parts:
– Sympathetic
– Parasympathetic
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Autonomic Nervous System
• Sympathetic – stimulates viscera
– Prepares the body for emergency situations
(“fight or flight” response to stress)
– Fear, emergency, physical exertion, and
embarrassment are responded to by this system
– This system shifts energy and blood toward the
skeletal muscles, cardiac muscles, and respiration
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Autonomic Nervous System
• Parasympathetic – inhibits viscera
– Energy conservation system
– Restores body energy during rest
– Responses toward digestion, elimination of waste,
and decreases heart rate
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The Neuron
The brain and spinal cord are made up of many cells, including neurons
and glial cells.
90% of the brain is glial cells; they provide support functions for the
neurons. Most neurons are comprised of four primary structures:
Soma: The soma is the cell body of the neuron.
Dendrites: The dendrites branch out from the soma resembling branches of a tree
(dendron is Greek for Tree).
Axon: The axon is a long, slender tube that carries information away from the soma to the
terminal buttons. Axons are usually covered by a myelinated sheath.
Terminal Buttons: secrete neurotransmitters which affects the receiving cell.
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Different Types Of Neurons
There are different types of neurons. They all carry electro-chemical nerve signals,
but differ in structure (the number of processes, or axons, emanating from the cell
body) and are found in different parts of the body.
Sensory neurons or Bipolar neurons carry messages from the body's sense
receptors (eyes, ears, etc.) to the Central Nervous system (CNS). These neurons
have two processes. Sensory neuron account for 0.9% of all neurons. (Examples
are retinal cells, olfactory epithelium cells.)
Motoneurons or Multipolar neurons carry signals from the CNS to the muscles
and glands. These neurons have many processes originating from the cell body.
Motoneurons account for 9% of all neurons. (Examples are spinal motor neurons,
pyramidal neurons, Purkinje cells.)
Interneurons or Pseudopolare (Spelling) cells form all the neural wiring within the
CNS. These have two axons (instead of an axon and a dendrite). One axon
communicates with the spinal cord; one with either the skin or muscle. These
neurons have two processes. (Examples are dorsal root ganglia cells.)
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Any man who reads too much and uses his
own brain too little falls into lazy habits of
thinking.
Albert Einstein
After Einstein passed away in 1955 at the age of 76, a Princeton University pathologist
named Thomas Harvey removed the physicist's brain during an autopsy, and kept it in
hopes of studying it to unlock the secret of Einstein's genius
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